Merge branch 'mm/detach-at-HEAD-reflog' into maint

After "git checkout --detach", "git status" reported a fairly
useless "HEAD detached at HEAD", instead of saying at which exact
commit.

* mm/detach-at-HEAD-reflog:
  status: don't say 'HEAD detached at HEAD'
  t3203: test 'detached at' after checkout --detach

wt-status.c

@@ -1319,6 +1319,12 @@ static int grab_1st_switch(unsigned char *osha1, unsigned char *nsha1,
 	hashcpy(cb->nsha1, nsha1);
 	for (end = target; *end && *end != '\n'; end++)
 		;
+	if (!memcmp(target, "HEAD", end - target)) {
+		/* HEAD is relative. Resolve it to the right reflog entry. */
+		strbuf_addstr(&cb->buf,
+			      find_unique_abbrev(nsha1, DEFAULT_ABBREV));
+		return 1;
+	}
 	strbuf_add(&cb->buf, target, end - target);
 	return 1;
 }